def p(n):
    for i in range(2, n):
        if n%i==0:
            return False
    return True

a = input().split()
a = "".join(a)
a = a.replace('zero', '0'). replace('one', '1'). replace('two', '2').replace('three', '3').replace('four', '4').replace('five', '5'). replace('six', '6').replace('seven', '7').replace('eight', '8'). replace('nine', '9')
a = int(a)
if a >= 100 and a <= 999:
    prost = []
    for i in range(2, 1500):
        if p(i):
            prost.append(i)
    mn = 10000
    k = 0
    for i in prost:
        if abs(i - a) < mn:
            mn = abs(i-a)
            k = i
    print(k)
else:
    print('Wrong input')
